All those strings had to be allocated somewhere. I went through my app and removed all those lovely descriptive messages. Instead I just logged the line number – that was enough to work out where it went wrong.

Use statics in moderation

Next I looked into how I was defining static variables. I like statics because they are only visible to the file in which they are declared: a primitive form of encapsulation. A typical C source file might have started with:

What matters is that I have four pointers and a short declared as statics, meaning I have a whole chunk of memory statically allocated just for this one file.

Powernoter is not a small app … this multiplied by tens of files means that I had a load of memory statically allocated, which was never used unless the user was actually invoking the functionality represented by those files.

I only allocate a NoteList when it is being used, and free it as soon as possible.

Omit needless code

Although the SDK includes definitions for things like DictationSession on Aplite, so that code can be compiled regardless of the platform (you do need to check return calls though), it made no sense to include that code at all. I #ifdefed whole chunks of code to reduce the app size:

Although I think I am a decent enough software engineer, I am under few illusions as to my abilities as a designer, which is why I let you choose your very own foreground and background colors in Powernoter, except if you are running on an original Pebble, in which case all that code, including the color names, is #ifdefed out.

Once upon a time were were limited to 120 or so bytes per message sent between the watch and the phone. I wrote inordinately complex code to page menu items in dynamically from the phone to the watch so that you could scroll through infinitely long menus. Then Pebble gave us what we wanted, with massive (8Kish) message buffers.

When you only have a little memory free to start with, the last thing you want to do is go allocating 8K buffers. It won’t work.

My code to determine the size of the input buffer looks like this now:

The LOW_MEMORY_DEVICE macro is set on Aplite only. Users on the original Pebble won’t see an enormous number of notes listed, or a lot of a note’s content, but at least they’ll see something.

Make long strings into Resources

There is an excellent Internationalization sample for the Pebble. Although Powernoter isn’t internationalized, there are no strings hardcoded in code … all strings are accessed via a single point. I include the strings in a single source file in the app, except for certain very long strings, such as the About page. These I load as resources from files:

Getting from 787 bytes free to 7,223 bytes free, so that Powernoter can really run on Aplite involved many changes, some which I’d say were generally good practice (reducing statics and instead using structs which are allocated/freed), and some less so (removing error log messages).

In general I don’t think the code looks too unreadable as a result of supporting Aplite … certainly I’d prefer not to have as many #ifdefs sprinkled throughout my code as I have, but it’s not that bad.

One thing is for sure, the changes I had to make to Powernoter to get it to run on Aplite are nothing compared with the miracles the Pebble team pulled to get the original Pebble to support the same SDK as Pebble Time and Pebble Time Round.